Feature Encoding. Following previous works [1]}, [2]}, we adopt the TSN [3]} and I3D [4]} for feature encoding.
For THUMOS14, the interval \(\sigma \)  is set to 8 and 5 for I3D and TSN respectively. We crop each video feature sequence with overlapped windows of size \(T = 256\)  and stride 128.
As for ActivityNet-1.3, the sampling frame stride is 16, and each video feature sequence is rescaled to \(T = 100\)  snippets using linear interpolation.
